Generally, an organic electronic device such as an organic light emitting device and an organic solar cell are very vulnerable to moisture and oxygen due to organic materials used therefor. In order to solve this problem, there have been developed various sealing techniques for suppressing infiltration of moisture and oxygen into an organic electronic device.
In the most common sealing technique used today, glass substrates are used. An upper glass substrate to which a moisture absorbent adheres is bonded to a lower substrate on which an organic electronic device is formed so as to block moisture and oxygen.
However, a sealing technique using glass substrates has been regarded as inappropriate for a next-generation organic electronic device since it uses expensive glass substrates and is not applicable to a large-sized substrate and flexibility required for a flexible organic electronic device cannot be obtained. In order to solve this problem, various thin film type sealing techniques have been developed actively.
A thin film type sealing technique can be wieldy applied to a method in which a sealing thin film for blocking gas is directly formed on a lower substrate on which an organic light emitting device, an organic solar cell, and the like are formed and a method in which a sealing thin film for blocking gas is formed on a polymer film and bonded thereto through lamination. Recently, the method for forming a laminated film-based gas blocking layer has been preferred since it is easier to obtain productivity and easily applicable to various organic electronic devices as compared with the method for forming a gas blocking layer directly on an organic electronic device.
In order to commercialize the thin film type sealing technique, a performance of a gas blocking layer for blocking moisture and an oxygen gas fundamentally needs to be obtained. Recently, a multilayered thin film-structured gas blocking layer formed by stacking two or more kinds of single gas blocking layers has been mainly studied and developed. Theoretically, if a single inorganic thin film made of Al2O3, SiO2 or SiNx can be formed in a high-density thin film without defects in process and defects within the thin film, the single inorganic thin film as a gas blocking layer for blocking moisture and an oxygen gas can be sufficient to obtain such a performance. However, is impossible to form a zero-defect thin film without cracks, pinholes, and the like by a typical inorganic thin film deposition method such as a sputtering method and a chemical vapor deposition method. Further, it is impossible to solve a problem of an infiltration path of moisture and an oxygen gas caused by a defect which may occur in a thin film to be formed depending on roughness of a substrate and a void formed at a boundary between crystals as a result of crystallization of the thin film with conventional inorganic thin film forming methods.
As a solution to this problem, an organic/inorganic mixed multilayer gas blocking layer of a stacked structure including an organic thin film and an inorganic thin film to form a high-performance gas blocking layer has been studied and developed actively.
The organic/inorganic mixed multilayer gas blocking layer is capable of greatly reducing moisture permeability by extending an infiltration path of moisture and an oxygen gas even if there is a defect at a certain level or less within the inorganic thin film and is very advantageous to obtain flexibility required for a flexible organic electronic device. Therefore, it has been regarded as appropriate for commercialization of a next-generation organic electronic device.
As a representative technique for forming an organic/inorganic mixed multilayer gas blocking layer, there is a gas blocking layer produced by Vitex Systems, Inc. (US). This gas blocking layer has been regarded as a unique technique capable of ensuring a long life of a next-generation high-performance organic electronic device such as a high-efficiency organic light emitting device among thin film type sealing techniques currently available.
However, if defects of an inorganic thin film cannot be fundamentally solved, a conventional organic/inorganic mixed multilayer gas blocking layer needs five or more stacked films to suppress infiltration of moisture and oxygen. Further, an atmospheric coating process and a vacuum deposition process need to be performed alternately for forming each of a buffering organic thin film and an inorganic gas blocking layer, and, thus, productivity can be decreased and manufacturing costs can be increased.
In particular, a gas blocking organic/inorganic thin film formed by a conventional vacuum deposition process and an atmospheric coating process is not sufficient to suppress infiltration of moisture and oxygen. Therefore, it needs to have organic/inorganic multilayer thin films stacked at least five or more times so as to be applied to a high-performance organic light emitting device. Thus, overall manufacturing costs of a blocking layer can be further increased and productivity can be further decreased.
Recently, in order to reduce the number of stacked organic/inorganic multilayer thin films, methods for forming a high-performance gas blocking layer using various deposition methods and various deposition materials have been studied actively. As a result of some studies using an Atomic Layer Deposition (ALD) method, formation of a high-performance gas blocking layer has been reported. However, the ALD method cannot be used as a commercialized technique in view of productivity and low manufacturing costs. According to some studies of forming a gas blocking layer based on a sputtering method and a CVD method, requirements in view of productivity and lower manufacturing costs can be easily satisfied but a gas blocking layer cannot be expected to be commercialized in view of performance.